The invention relates generally to data recovery from optical media storage systems, and more particularly to methods and apparatuses for data recovery in the absence of threshold detection.
Advances in manufacturing technologies and system architecture have led to increasingly powerful consumer electronic devices and computers. These consumer electronic devices and computers support features and applications, such as multimedia presentations, in connection with which vast amounts of information are processed and stored. Generally, the amount of information is not only vast, but also ever-increasing.
To provide the information, optical storage and retrieval systems have been developed, including in the form of optical disk drives and media. To provide ever-increasing amounts of information, these optical storage and retrieval systems require ongoing improvements that overcome factors limiting system capacity, including, among other things, improving detection of recorded information.
Detection of recorded information is conventionally accomplished using a threshold. More specifically, channel bits of an optical read channel (using, for example, 1,7 run-length-limited modulation coding) are detected by comparing a read signal to a predetermined threshold: if the read signal exceeds the threshold at a particular channel-bit location, that channel-bit is considered a `1`; otherwise the channel-bit is considered a `0`.
Detection against a threshold relies on appropriately setting the threshold. Generally, the threshold is set toward recovering data from the recording media within an acceptable bit error rate. To do so, the threshold optimally is set to the center of an "eye-pattern", the eye-pattern being a measure that indicates the amplitude and phase margins of the read signal. However, the read signal's amplitude and phase margins tend to be affected by various parameters, including, among others, the write power, the write sensitivity of the media, the quality of the optical spot of the write and read drives, the focus offset of the write and read drives, and the recording density (on optical disk media, recording density varies with radial position). Because these parameters vary across systems and media, the center of the eye pattern tends to vary and, in turn, the optimal threshold setting tends to vary. Being subject to such variations, threshold detection technologies are limited.
Accordingly, it is desirable to provide a method and apparatus that, in detection, overcomes conventional technologies' reliance on threshold setting.